1. Field of the Invention
This invention relates to wall thickness measuring apparatus and/or method, in general. More specifically, it concerns a pulse-echo acoustic system for measuring wall thickness and simultaneously determining presence of anomalies in the wall being surveyed.
2. Description of the Prior Art
Heretofore, acoustic pulse-echo type measurements have been employed for wall thickness non-destructive measurements and there are two U.S. Pat. Nos. 3,995,179 issued Nov. 30, 1976, and 4,022,055 issued May 10, 1977, both of which are assigned to the same assignee as this application. These patents describe piezoelectric transducer structure which was employed in making the type of wall thickness measurements that are of concern in this application. However, the earlier patent dealt with the need for dissipating or damping the acoustic energies from one side of a piezoelectric crystal in order to avoid the interfering signals generated at the back face of the crystal. And, the later of those two patents showed and described a structure for splitting the energy that was transmitted from a transducer in order to have one portion directed normally to the wall to be measured while the other portion is directed at an acute angle for discovering anomalies that may exist in the wall of a pipe or the like being measured.
Although there exists a U.S. patent to Sansom, U.S. Pat. No. 3,106,839 issued Oct. 15, 1963, it discloses a wheel with a rubber tire exterior which was designed to ride upon the surface of a rail such as a railroad rail or the like. And, energies from a transducer are reflected down to the same location at the base of the wheel. Therefore, it is not applicable to the type of wall thickness measurement and simultaneous surveying that the applicant's invention is concerned with.